Graduation date: 1998

Thèse doctorat : Automatique Industrielle : Villeurbanne, INSA : 2005. / Thèse rédigée en anglais. Résumé étendu en français. Titre provenant de l'écran-titre. Bibliogr. p. 155-167.

Woody plant encroachment, that is, a substantial increase in the abundance of woody plants in a grassland or savanna, occurs in many parts of the world. It often has large effects on plant and animal populations and communities and on ecosystem properties and processes. However, little is known about the dynamics of woody plant encroachment and how these are affected by soils, by topography, and by the spatial pattern of the vegetation. Encroachment in turn can affect the spatial pattern of the vegetation. Using data from historical aerial photographs, I measured changes in woody plant cover and constructed, parameterized and compared a set of dynamic models of woody plant encroachment in central Texas savannas. These models predicted final woody cover from initial woody cover and the initial spatial configuration of woody plants. Then I incorporated soil and topography into these models to determine their effects. Finally, I examined the effects of encroachment on the spatial pattern of the vegetation. Incorporating negative density dependence in our models improved their fit, demonstrating that encroachment is density-dependent. A function that predicted the formation of new woody patches from a density-independent seed supply also improved the models' performance. The improvement in the models that resulted from incorporating the total length of woody-herbaceous edges confirmed that encroachment in this system occurs in part by the outward expansion of woody patches. The spatial pattern of the vegetation changed during woody plant encroachment. Spatial pattern (measured as degree of fragmentation) often had a non-linear relationship with cover. Furthermore, the spatial heterogeneity in fragmentation, that is, plot-to-plot variation in the degree of fragmentation, also changed during encroachment. Topography and soil type had, in general, little effect the dynamics of woody plant encroachment. Therefore, a relatively simple model of woody plant encroachment provided good predictions of woody cover at the end of the time periods. Other systems experiencing woody plant encroachment, forest succession, or invasion by non-native plants could be modeled using the same approach. / text

Kommt es zu einer akuten respiratorischen Insuffizienz, stellt die Beatmung einen wichtigen Eckpfeiler der Therapie dar. Da eine invasive Beatmung über einen endotrachealen Tubus mit Risiken verbunden ist, sollte wann immer möglich, eine nicht-invasive Beatmung eingesetzt werden. Neben den absoluten Kontraindikationen limitieren Undichtigkeit, Ulzerationen im Gesichtsbereich und ein schlechter Tragekomfort die Praktikabilität der Gesichtsmasken. Ziel dieser Arbeit war die Evaluation eines neuartigen Beatmungshelms in einem Lungenmodell und einer Probandenstudie im Hinblick auf Beatmungsparameter (Beatmungsdruck, AZV, AMV, PEEP) Resistance, Compliance, Delay-Zeiten, CO2, SpO2, Triggerzeit und Komfort. Es zeigte sich, dass eine Steigerung des PEEP auf 8 mbar zu einer signifikanten Reduktion der DelayTrigger und DelayPeep-Zeiten führte. Höhere PEEP-Werte gingen hingegen mit einer zunehmenden Leckage und Gefahr einer Desynchronität zwischen Proband und Ventilator einher. Eine zusätzliche Druckunterstützung konnte das AMVLunge signifikant steigern, was zu einem Abfall der CO2-Konzentration sowohl in der transkutanen Messung als auch im Helm führte. Problematisch zeigte sich aufgrund der Compliance des Helms, dass ein hoher Anteil des AMV zum Druckaufbau im Helm verloren geht. Dieser Effekt war abhängig von PEEP, ASB sowie Compliance und Resistance der Lunge. Der Beatmungshelm ist als eine gute Alternative zu betrachten, wenn eine Aufrecherhaltung eines PEEPs im Vordergrund steht, wie etwa bei einer Oxygenierungstörung bei Parenchymversagen.

Invasive alien species (IAS) pose a serious threat to ecosystems and societies worldwide. Local ecological knowledge (LEK) is increasingly valued as a means of understanding environmental issues; however, its application in the context of IAS research has been limited. The overall objective of this study was to document the LEK of farmers and Weed Supervisors to gain insight into a recent IAS, Odontites serotina. I conducted semi-structured interviews with farmers and Weed Supervisors with O. serotina management experience. Results indicated that the socio-economic impacts for farmers were severe in affected rural communities. However, participants had developed promising control techniques, including the application of compost mulch. I used this LEK as well as data on species occurrence, environmental variables, and measures of propagule pressure to forecast the potential distribution of O. serotina across Manitoba. The risk map generated will be useful for guiding future monitoring and public outreach efforts.

Invasive alien species (IAS) pose a serious threat to ecosystems and societies worldwide. Local ecological knowledge (LEK) is increasingly valued as a means of understanding environmental issues; however, its application in the context of IAS research has been limited. The overall objective of this study was to document the LEK of farmers and Weed Supervisors to gain insight into a recent IAS, Odontites serotina. I conducted semi-structured interviews with farmers and Weed Supervisors with O. serotina management experience. Results indicated that the socio-economic impacts for farmers were severe in affected rural communities. However, participants had developed promising control techniques, including the application of compost mulch. I used this LEK as well as data on species occurrence, environmental variables, and measures of propagule pressure to forecast the potential distribution of O. serotina across Manitoba. The risk map generated will be useful for guiding future monitoring and public outreach efforts.

Thesis (Ph.D.)--University of Wollongong, School of Biological Sciences. / Typescript. Includes bibliographical references: leaf 161-203.

Thesis (Ph.D.)--Mississippi State University. Department of Biological Sciences. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--Montana State University--Bozeman, 2004. / Typescript. Chairperson, Graduate Committee: Roger L. Sheley. Includes bibliographical references (leaves 26-30).

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 33-43). Also available on the World Wide Web.